Functional near infra-red spectroscopy (fNIR) is a non-invasive imaging method involving the quantification of chromophore concentration resolved from the measurement of near infrared (NIR) light attenuation, temporal or phasic changes. fNIR may be used to detect brain activity (i.e., neural load) by measuring blood oxygenation levels in the brain as an indicator of brain activity in a local area. Specifically, fNIR may use infrared light emitting diodes (LEDs) at two different wavelengths to detect the blood oxygenation levels needed to determine brain activity. The infrared (IR) wavelengths are chosen to be within the IR “window” of tissue, skin, and bone (e.g., 700 nm-900 nm) and to correspond to the IR absorption by hemoglobin and oxygenated hemoglobin. A change in the concentration levels of hemoglobin and oxygenated hemoglobin may be determined using the modified Beer-Lambert law: OD=−log(I/Io)=ε[X]d×DPF+G where OD is the optical density of the sample as determined from the negative log ratio of the detected intensity of light I with respect to the incident intensity of light Io. The OD is related to the absorption coefficient of the tissue ε, [X] is the chromophore concentration, and d is the net distance traveled by the light from the source to the detector scaled by the differential path-length factor DPF, plus a geometry factor G.